ipv6: sr: fix possible use-after-free and null-ptr-deref

The pernet operations structure for the subsystem must be registered
before registering the generic netlink family.

Fixes: 915d7e5 ("ipv6: sr: add code base for control plane support of SR-IPv6")
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
Link: https://lore.kernel.org/r/20240215202717.29815-1-kovalev@altlinux.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: kovalev0

net/ipv6/seg6.c

@@ -512,22 +512,24 @@ int __init seg6_init(void)
 {
 	int err;
 
-	err = genl_register_family(&seg6_genl_family);
+	err = register_pernet_subsys(&ip6_segments_ops);
 	if (err)
 		goto out;
 
-	err = register_pernet_subsys(&ip6_segments_ops);
+	err = genl_register_family(&seg6_genl_family);
 	if (err)
-		goto out_unregister_genl;
+		goto out_unregister_pernet;
 
 #ifdef CONFIG_IPV6_SEG6_LWTUNNEL
 	err = seg6_iptunnel_init();
 	if (err)
-		goto out_unregister_pernet;
+		goto out_unregister_genl;
 
 	err = seg6_local_init();
-	if (err)
-		goto out_unregister_pernet;
+	if (err) {
+		seg6_iptunnel_exit();
+		goto out_unregister_genl;
+	}
 #endif
 
 #ifdef CONFIG_IPV6_SEG6_HMAC
@@ -548,11 +550,11 @@ int __init seg6_init(void)
 #endif
 #endif
 #ifdef CONFIG_IPV6_SEG6_LWTUNNEL
-out_unregister_pernet:
-	unregister_pernet_subsys(&ip6_segments_ops);
-#endif
 out_unregister_genl:
 	genl_unregister_family(&seg6_genl_family);
+#endif
+out_unregister_pernet:
+	unregister_pernet_subsys(&ip6_segments_ops);
 	goto out;
 }